1. Field of the invention:
This invention relates to a high output power semiconductor laser apparatus containing a semiconductor laser array device therein in which the adjacent laser operation areas are optically coupled with a 180.degree. degrees phase shift therebetween.
2. Description of the prior art:
Semiconductor laser devices which are useful as light sources for information processing apparatus such as optical discs, laser beam printers, etc., have been put into practical use. With an increase in information to be processed, speed is required, and the development of semiconductor devices which can produce the highest possible output power but which can retain stabilized operation characteristics has begun. Even semiconductor laser devices having a single active region, the development of which has been most advanced, can only produce an output power of approximately 50 mW at the maximum value in practical use.
Semiconductor laser arrays (including gain guided laser arrays and index guided laser arrays) have been proposed in which a plurality of laser operation areas are disposed in a parallel manner to attain optical phase coupling therebetween resulting in a laser array device producing great output power with a single phase. However, in conventional gain guided laser arrays, the laser operation areas of which attain a gain-guiding function, phase variation arises in each of the laser operation areas and moreover loss of light increases with a decrease in a gain in the phase coupling region positioned between the adjacent laser operation areas, so that a phase shift of the electric field between the adjacent laser operation areas reaches 180.degree..
For conventional index guided laser arrays, a CSP-LOC (channeled-substrate planer large-optical-cavity) laser device has been proposed by D. Botez et al., of RCA Laboratories, Fourth International Conference on Integrated Optics and Optical Fiber Communication, Abstract 29B5-2, June 27-30, 1983 Tokyo, Japan, and a ridged laser array device has been proposed by D. E. Ackley et al., Hewlett Packard Laboratories, Appln. Phys. Letters, 42(2), 15, p. 152, January 1983. Both of these laser array devices have the disadvantage that laser light at the region between the adjacent laser operation areas is absorbed into the electrode to a great extent due to the built-in structure thereof for constituting the index guided laser array, resulting in a 180.degree. phase shift between the adjacent laser operation areas.
Thus, conventional semiconductor laser arrays cannot attain stabilized oscillation with a 0.degree. phase shift between the adjacent laser operation areas, but they can attain the stabilized oscillation only with a 180.degree. phase shift therebetween. Moreover, laser beams are emitted from the facet of the laser array device at a certain angle in each of the two different directions with respect to a direction which is vertical to the surface of the facet, so that the laser oscillation produced by these conventional laser array devices cannot be utilized in various instruments although it has a high output power.